1. Field Of the Invention
This invention in general relates to the field of optical recording systems and media and, in particular, to storage media comprising optically differentiated or discriminated data sites by which means a greater resolution and storage density is attained.
2. Description of the Prior Art
Technical data relevant to the present application can be found in sources such as:
Optical Physics, Lipson and Lipson, Cambridge University Press, 1969. PA0 Optical Materials, S. Musikant, Marcel Dekker, Inc., New York, 1985. P. 64-76. PA0 Guerra, J. M., Phase Controlled Evanescent Field Systems and Methods for Optical Recording and Retrieval, U.S. Pat. No. 5,754,514, issued May 19, 1998.
Conventional optical storage media commonly use a "land and groove" configuration in which alternating data tracks are separated in height by .lambda./6, where .lambda. is the illumination wavelength. The purpose of this height differentiation between tracks is to cause destructive interference, or cancellation, of the ringing caused by the coherent illumination, thereby allowing spacing, or track pitch, that is closer to the resolution limit of an incoherently illuminated system. However, the alternating height is usually binary, and does not allow super-resolution (i.e. track separation smaller than the resolution limit of the optical system).
Other examples of differentiated tracks or sites include the red, green, and blue color filter stripes or dot matrix such as found in color television monitors, and similar red, green, and blue color stripes in Polaroid's.TM. instant color slide film and Polavision.TM. instant movie film. In both cases, the purpose of the color stiripes was to cause selective local color change from white to black and any shade of color in between by combining one or all of the RGB color elements in various intensity combinations. However, in neither example was the intent or effect to cause super-resolution, nor means for optical data storage in the case of the former.
U.S. Pat. No. 5,910,940 issued Jun. 8, 1999, "Optical Recording Systems and Media with Integral Near-Field Optics" issued to Guerra discloses optical storage media having an integral micro-optical structure to effect higher resolution. In part, the higher resolution results from the larger system numerical aperture tht is obtained by combining the micro-optics in the medium with the drive objective optics. This larger numerical aperture allows the higher spatial frequencies contained in the evanescent, or "near-field," to contribute to the image, thereby increasing resolution and storage density.